(1) Field of the Invention
The present invention relates to a locking device for locking a pivotable head of a hand tool and the pawl of the device is well positioned during operation and the parts of the device are easily manufactured.
(2) Description of the Prior Art
A conventional locking device for locking pivotable head of a hand tool is disclosed in U.S. Pat. No. 5,199,335. However, the locking device of U.S. Pat. No. 5,199,335 includes inherent shortcomings which make the hand tool to be difficult manufactured and the main part tends to shake. The locking spool includes teeth defined in the shank thereof and the teeth are defined along inward curved surface which makes the teeth to be difficult to be manufactured. Because of the difficulties of manufacture of the teeth defined in the locking spool, the teeth might not be perfectly engaged with the teeth of hub of the tool head. This might lead unstable operation of the tool head. Besides, the recess of the yoke is too long so that the lugs of the yoke might be deformed during quenching process and the head tool might shake during operation. The teeth of the locking spool are opened to outside of the hand tool and foreign objects such as metal debris or dust might be attached to the teeth and affect the locking feature. Furthermore, the bead is directly engaged with the teeth of the locking spool so that the bead might be engaged with the root of the teeth or positioned on a peak of one of the teeth. The precision of locking feature is not satisfied.
The present invention intends to provide a locking device which is located in the handle and the movement of the pawl to move to engage with or disengage from the too head is precisely controlled by the switch member which includes a curved surface which pushes the pawl toward the tool head and a flat surface which allows the pawl to be pushed by a spring and away from the tool head.